The invention relates to an actuation system for a drive unit of a motor vehicle
German patent document DE 10 2005 048 330, which is currently unpublished, discloses an actuation system for an electric machine, having a function level and a monitoring level which is independent of the function level. The function level has a device for converting one or more incoming operating parameter values of the electric machine into an output value. An actual torque is output as an output value via the function monitoring level.
German patent document DE 102 51 095 A1, on the other hand, discloses a method for operating an electric machine having an actuation system. An operating variable of the electric machine or of the actuation system is monitored, and the acceptability of an actual torque of the electric machine is checked. When the actual torque is not acceptable, a fault reaction is initiated. The acceptability of the actual torque is preferably checked by forming an acceptable torque from a setpoint torque and predefined limiting values for the setpoint torque. The actual torque is acceptable if its deviation from the acceptable torque does not exceed a specific absolute value. The invention can be used to monitor an electric machine which is employed as a starter/generator in a motor vehicle.
The control units of an actuation system of a drive unit are generally monitored on three levels. Such a monitoring concept is disclosed, for example, in German patent document DE 44 38 714 A1, which describes a method and apparatus for controlling the drive power of a vehicle having a microcomputer with at least two different levels. A first level carries out the control functions, while a second level performs the monitoring functions. A third level forms a supervision level which supervises the monitoring level and thus the microcomputer.
One object of the present invention is to provide an actuation system with a high level of data security, as well as a good reaction speed and availability level.
This and other objects and advantages are achieved by the method and apparatus according to the invention, in which a data transmission device for outputting data to a data bus is arranged in the function monitoring level. The data transmission device can output a drive setpoint torque to the drive unit, to actuators or sensors which are assigned to it or to a power output stage of a second drive unit.
By arranging a data transmission device for outputting data in the function monitoring level, the data can be subjected to quality checking by the function monitoring level, before they are output. For example, the data can be checked for up-to-dateness, acceptability, plausibility, correctness of an accompanying check number and the like. Likewise, this permits unacceptable data to be replaced by acceptable data, thereby increasing the data security and the quality of the data which is output. Carrying out these processes which require computer capacity and are time consuming in the function monitoring level speeds up the processes in the function level. At the same time, the desired quality of the data transmission is maintained since supervision processes and check processes which are relevant to quality are not omitted, rather, they are simply exported into the function monitoring level.
In one embodiment, a predefined setpoint value can be fed to the control unit and split in the function level of the control unit into a plurality of drive setpoint torques. Each drive setpoint torque is assigned to a separate drive unit, so that it is possible to coordinate a plurality of drive units with one another. With this embodiment, the failure of one drive unit can easily be compensated by the other drive units.
In another embodiment, the control unit has a torque limiter by which the drive setpoint torque which is fed to it can be limited if a comparator detects that the sum of the drive setpoint torques exceeds a maximum acceptable torque. This ensures that a fault has not occurred when the torque request was split and that the sum of all the torques also corresponds to the desired overall torque.
In still another embodiment, the data transmission device of the function monitoring level of the control unit which is assigned to a drive unit can output a setpoint axial torque to a hybrid control unit. As a result, it is possible to form a distributed system in which the control of the actuators occurs locally with respect to the actuators (because, for example, the power electronics including the control means are arranged directly on the machine). In this case, there is no need for cables for the machine, but instead it is also possible to use power rail arrangements. The power rail arrangements here are rigid conductor tracks which are cost effective to manufacture and robust against heat, moisture, dirt and mechanical loading.
In yet another embodiment, a hybrid control unit is provided in which drive setpoint torques for the separate drive units that are to be actuated can be formed from a requested axial setpoint torque. The drive setpoint torques can be forwarded from the hybrid control unit to the control units of the drive units which are to be actuated. This embodiment has the advantage that a separate hybrid control unit is provided to coordinate all the drive units. The control unit of the internal combustion engine is therefore relieved of these functions and decoupled from the associated risk of faults. Different drive units, for example even a plurality of internal combustion engines, can therefore be coupled to a hybrid control unit. If a fault occurs in the hybrid control unit, it is possible to deactivate the hybrid control unit and operate the internal combustion engine solely by means of its own control unit. This increases the availability level of the entire motor vehicle system.
In another embodiment, the control units of the drive units which are to be actuated are connected to the hybrid control unit in such a way that the respective actual torques of the separate drive units can be forwarded from the control units of the drive units to the hybrid control unit. It is therefore possible for the hybrid control unit to monitor the satisfactory implementation of the specified tasks, and if appropriate, to intervene in a controlling fashion.
In a further embodiment, an acceptable torque can be formed in the function monitoring level of the control unit and increased by a tolerance T. This toleranced acceptable torque can be compared in a second torque comparator with a sum which can be formed by adding the respective actual torques or the actual axial torques of the separate drive units, and a remedial measure can be triggered by the second torque comparator if this sum exceeds the toleranced acceptable torque. As a result, it is possible to detect a fault in the composite actual torque, and to initiate measures for fault correction. Monitoring the composite actual torque improves the fault detection. This only requires monitoring of the composite torque since it influences the reaction of the vehicle to undesired positive or negative acceleration. However, it is not necessary to monitor the distribution of the individual torques. Initiating the remedial measures ensures that there is no undesired reaction of the vehicle, for example due to excessive torque or an excessively high braking torque. Since it continues to be possible to use the system even as a result of these measures, the availability level of the drive units and of the entire system increases.
In still a further embodiment, a supervision unit which supervises the function level and/or the function monitoring level of the hybrid control unit is assigned to the hybrid control unit. The supervision unit is directly connected to the data transmission device via a deactivation path, and the data transmission device can be deactivated if the supervision unit detects a fault of the hybrid control unit. The use of a three level monitoring concept improves the quality of the data and enhances the detection of faults.
In yet another embodiment, the supervision unit is directly connected to a power output stage of one of the control units via a deactivation path, and the power output stage can be deactivated if the supervision unit detects a fault of the control unit. It is therefore possible, for example, to deactivate the power output stages of electric drive units or actuators of an internal combustion engine if a supervision unit of a hybrid control unit detects a fault of the hybrid control unit. It is also possible to avoid potential damage to the drive units due to incorrect actuation.
In one embodiment, the supervision unit is directly connected to the hybrid control unit via a reset path, and the hybrid control unit can be reset into a standard state if the supervision unit detects a fault of the hybrid control unit. As a result, in the event of a fault the actuation system can be returned to a defined state. This increases the availability level of the system.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.